This application is based on and claims priority to Japanese Patent Application No. 2001-193862, filed on Jun. 27, 2001, the entire contents of which is hereby expressly incorporated by reference.
1. Field of the Invention
This invention relates to an engine for an outboard motor and more particularly to an improved lubrication system for an outboard motor.
2. Description of the Related Art
Outboard motors typically have an internal combustion engine that is coupled to a propulsion unit, such as a propeller, for propelling the boat through the water. The internal combustion engine includes one or more pistons reciprocally connected to a crankshaft for rotation during the combustion process. The crankshaft, in turn, is typically spline-coupled to a driveshaft that transmits the engine torque through a bevel-gear transmission and to a propeller shaft which carries the propeller. Thus, the engine output is transmitted from the crankshaft to the driveshaft and ultimately to the propeller.
The typical outboard motor utilizes a spline-coupling to connect the male driveshaft spline to the female crankshaft spline. In order to maintain a smooth engagement in the coupling, grease is typically packed into and around the coupling. The coupling is usually re-packed during routine maintenance, which requires the driveshaft to be uncoupled and removed from the crankshaft. Once grease is packed into the coupling, the driveshaft is reconnected to the crankshaft via the spline coupling. During normal use, however, the grease may lose its efficacy and may dry, thus leaving the coupling dry and unlubricated, which can damage the coupling, either because of burning and/or rusting.
An aspect of the present invention involves an outboard motor comprising an internal combustion engine having a lubrication system for lubricating a coupling between the engine""s crankshaft and a driveshaft of the outboard motor. The engine includes a cylinder bore that defines in part a combustion chamber and a piston that is disposed within the cylinder bore and is connected to the crankshaft. The crankshaft is journaled for rotation at least partially within a crankcase. The driveshaft is coupled to the crankshaft through a spline coupling and is also operatively coupled to a propulsion device. The lubrication system comprises a passageway that extends through the crankshaft and communicates with the crankcase and with an area in which the spline coupling is disposed. Lubricant flows through the passageway from the crankcase to the spline coupling in order to lubricate the coupling.
In accordance with another aspect of the present invention, a lubrication system for a coupling between an engine output shaft and a driven shaft is provided. The engine includes a chamber in which at least a portion of the engine output shaft is disposed. The lubrication system comprises a passageway through the output shaft which communicates with the chamber of the engine and with an area in which the coupling is disposed. The passageway is arranged such that lubricant flows through the passageway from the chamber to the coupling.
An additional aspect of the present invention involves an outboard motor lubricant delivery system. The lubrication system comprises a passageway that has a first end in fluid communication with a chamber of an engine and a second end in fluid communication with an area to be lubricated. The chamber contains lubricant. The passageway is formed substantially along a longitudinal axis of a crankshaft of the engine. A metering device is provided between the chamber and the area to be lubricated to control the rate of lubricant delivery from the chamber to the area.